The news broke last night. Politicians in Wales fought to claim the credit for the windfall and were perhaps daydreaming of how they would spend the extra cash.

Except, according to the Treasury, it isn't true. The Welsh government appears to have got the wrong end of the stick. Wales's share of higher transport spending - the "Barnett consequentials" in the jargon - is not due to HS2 spending.

A Treasury spokesperson told me: "At the spending round, Wales received Barnett consequentials in the normal way; this excluded funding for HS2.

"The government is clear HS2 will be a vital part of our national infrastructure, boosting regional growth across the country and providing vital capacity the UK needs to compete in the global race.

"As with any government spending Barnett consequentials will be considered at the next spending review."

It appears that any increase in Wales's share of UK transport spending is down to the Treasury agreeing to fund major road schemes in England - and nothing to do with HS2, which is excluded from the calculations.

Plaid Cymru now say the Treasury statement raises questions about the finance minister's competence. The Welsh Liberal Democrats, who announced the news last night, are trying to get to the bottom of "some misunderstanding".

Either the Treasury - which holds the purse strings - or the finance minister has got it wrong. They can't both be right, which means a politician or two will end up with egg on their face and awkward questions to answer.